Boughton adapted his own libretto from the play of the same name by Fiona MacLeod, a pseudonym of writer William Sharp.
The fairy people are not mischievous, childlike sprites, but are proud and powerful: immortal demigods who are feared by mortals and who can (and do) interfere with the lives of men and women.
Alternatively, the progression of Etain into the mortal realm and her pursuit and redemption by Midir have similarities with the legend of Orpheus and Eurydice.
[5] In 1921, Penelope Spencer was engaged by Boughton to stage dances and choruses for the Glastonbury Festival, some of which he incorporated into this opera.
Speaking in 1949, Sir Arthur Bliss said "I remember vividly how Boughton made his characters live, and the masterly effect of the choral writing".
He is known as the Amadan-Dhu, the Faery Fool, the Dark One, and is an agent of unseen and fateful powers, whose touch brings madness and death to mortals.
A woman's voice is heard and Etain enters the clearing, looking bewildered and singing about the wonderful place she came from, where death is only a "drifting shadow" and where the Faery folk - the Shee - hold court.
Dalua realises that the reason for their meeting is now clear to him; a mortal king has sought immortal love and is led towards them under similar compulsion to theirs.
Spirit voices warn Eochaidh to return to his people, but by then he is under Dalua's spell and follows him blindly into the wood.
As soon as she has retired to her room, a stranger appears at the door - Midir, Etain's immortal lover, disguised as a harpist.
The song "How beautiful they are" appears first in a chorus by unseen spirits, then is reprised by Midir of the "Shee" (Tuatha Dé Danann) as a solo aria accompanied by a harp.